Phase shift keying wireless communication apparatus and method

ABSTRACT

A baseband processor including an analog to digital converter configured to convert a baseband signal from an analog format into a corresponding digital format, wherein the baseband signal comprises a data packet having i) a preamble portion, ii) a header portion, and iii) a payload portion, wherein the payload portion of the data packet is in accordance with either i) a first format or ii) a second format. The baseband processor further includes a first demodulation pathway configured to recover i) the preamble portion of the data packet, ii) the header portion of the data packet, and iii) the payload portion of the data packet in response to the payload portion of the data packet being of the first format; and a second demodulation pathway configured to recover the payload portion of the data packet in response to the payload portion of the data packet being of the second format.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present disclosure is a continuation of U.S. application Ser. No.12,437,090, filed on May 7, 2009, which is a divisional of U.S.application Ser. No. 11/511,044 (now U.S. Pat. No. 7,539,266), filed onAug. 28, 2006, which is a continuation of U.S. application Ser. No.10/183,814 (now U.S. Pat. No. 7,106,803), filed on Jun. 26, 2002.

TECHNICAL FIELD

This invention is generally directed to communications technology, andis particularly concerned with systems and techniques for high effectivethroughput wireless data communications using phase shift keying (“PSK”)modulation.

BACKGROUND

The past few years has witnessed the ever-increasing availability ofrelatively cheap, low power wireless data communication services,networks and devices, promising near wire speed transmission andreliability. One technology in particular, described in the IEEEStandard 802.11b-1999 Supplement to the ANSI/IEEE Standard 802.11, 1999edition, collectively incorporated herein fully by reference, and morecommonly referred to as “802.11b” or “WiFi”, has become the darling ofthe information technology industry and computer enthusiasts alike as awired LAN/WAN alternative because of its potential 11 Mbps effectivethroughput, ease of installation and use, and transceiver componentcosts make it a real and convenient alternative to wired 10 BaseTEthernet and other cabled data networking alternatives. With 802.11b,workgroup-sized networks can now be deployed in a building in minutes, acampus in days instead of weeks since the demanding task of pullingcable and wiring existing structures is eliminated. Moreover, 802.11bcompliant wireless networking equipment is backwards compatible with theearlier 802.11 1M/2 Mbps throughput standard, thereby further reducingdeployment costs in legacy wireless systems.

802.11b achieves relatively high payload data transmission rates oreffective throughput via the use of orthogonal class modulation ingeneral, and, more particularly, 8-chip complementary code keying(“CCK”) and a 11 MHz chipping rate to bear the payload. As such,previously whitened or scrambled bitstream data of interest is mappedinto nearly orthogonal sequences (or CCK code symbols) to betransmitted, where each chip of the CCK code symbol is quaternary phasemodulated using QPSK (“quadrature phase shift keying”) modulationtechniques. Meanwhile the common phase of each CCK symbol is jointlydetermined by the current and previous symbols using differential QPSKor DQPSK modulation scheme. Subsequent conversion into the analog domainprepares these CCK symbols for delivery over a wireless medium RFmodulated on a carrier frequency within the internationally recognized2.4 GHz ISM band to form the payload or PLCP Service Data Unit of an802.11b complaint Physical Layer Convergence Procedure (“PLCP”) frame.The high-rate physical layer PLCP preamble and header portions are stillmodulated using the 802.11 compliant Barker spreading sequence at an 11MHz chipping rate. In particular, the preamble (long format—144 bits,short format—72 bits) is universally modulated using DBPSK(“differential binary phase shift keying”) modulation resulting in a 1Mbps effective throughput, while the header portion may be modulatedusing either DBPSK (long preamble format) or DQPSK (short preambleformat) to achieve a 2 Mbps effective throughput.

An IEEE 802.11b compliant receiver receives and downconverts an incidentinbound RF signal to recover an analog baseband signal bearing the PLCPframe, and then digitizes and despreads this signal to recover theconstituent PLCP preamble, header and payload portions in sequence. Thepreamble and header portions are Barker correlated and then either DBPSKor DQPSK demodulated based on the preamble format used to recoversynchronization data and definitional information concerning thereceived PLCP frame, including the data rate (Signal field in the PLCPheader) and octet length (Length field in the PLCP header) of thevariable-length payload or PSDU portion. The CCK encoded symbols formingthe PLCP payload portion are each correlated against 64 candidatewaveforms in received per symbol sequence in combination with DQPSKdemodulation to verify and reverse map each into the underlyingbitstream data of interest, at either 4 bits per symbol (5.5 Mbps) or 8bits per symbol (11 Mbps) increments.

The major benefit CCK offers is strong inherent resistance to multipathinterference, which is likely to be encountered in in-buildingtransceiver deployment. However, in an effort to match occupied channelbandwidth of legacy base 802.11 systems, 802.11b compliant CCKmodulation uses the same 11 MHz chipping rate, thereby limitingeffective throughput to a maximum 11 Mbps effective data throughput.While acceptable for some applications, this data rate is deemed tooslow for certain “broadband” applications such as full-screen streamingvideo and interactive gaming. 802.11b's sibling communications scheme,defined in the 1999 IEEE 802.11a Supplement to the ANSI/IEEE Standard802.11, 1999 edition (“802.11a”) offers a higher effective throughput(up to 54 Mbps), but sacrifices backwards compatibility with 802.11b,and requires data transmission in the 5 GHz band which is not generallyavailable outside North America. The forthcoming IEEE 802.11g high-ratePHY extension attempts to address 802.11a's backwards compatibilityissue through specifying dual 802.11b and 802.11a complianttransceivers, but this adds cost, complexity and power consumption tothe very price sensitive, consumer-oriented mobile devices which standto benefit most from high speed wireless data communications.

Accordingly, it would be advantageous to define a wireless datacommunications scheme which economically increases effective throughputover 802.11b compliant devices while maintaining backwards compatibilitywith such devices, thereby fully leveraging the worldwide benefits ofISM transmission and a large installed base of 802.11b systems.

SUMMARY

The present invention is directed in part to a baseband processor andassociated method suitable for use in a wireless transmitter. Thisprocessor and method utilizes packet header generation unit capable ofgenerating a header portion of an outbound data packet, PSK modulationcapable of PSK modulating the header portion at a first effectivethroughput and PSK modulating outbound data at a second effectivethroughput to form a PSK modulated payload (in which the secondeffective throughput is at least five times the first effectivethroughput), symbol modulation capable of symbol modulating the outbounddata at a third effective throughput to form a symbol modulated payload(in which the third effective throughput being less than the secondeffective throughput), and modulation selection capable of selecting oneof the PSK modulated payload and the symbol modulated payload to form apayload portion of the outbound data packet.

In accordance with an embodiment of the invention, a common PSKmodulation arrangement may be provided to economically handle bothheader and payload modulation. In an alternative embodiment, dedicatedmodulation units may be provided, if for example, a single PSKmodulation arrangement provides unacceptable performance.

Further, one or more disclosed embodiments make use of the DQPSK form ofPSK modulation to increase effective throughput at least twice that ofthe third effective throughput where symbol modulation utilizesorthogonal class symbol modulation such as CCK modulation. As such, aDQPSK modulator may be selectively clocked at the CCK chipping rate toachieve such effective throughput.

The present invention is also directed in part to a baseband processorand associated method suitable for use in a wireless receiver. Suchprocessor and method includes header demodulation capable of recoveringof a header portion of an inbound data packet, along with packetdemodulation capable of 1) recovering first data at a first effectivethroughput from the payload portion of the data packet according to asymbol demodulation scheme; 2) recovering second data from this payloadportion at a second effective throughput exceeding the first effectivethroughput according to a PSK demodulation scheme; and 3) selecting oneof the first and second data as inbound data presented in the payloadportion of the inbound data packet based on the recovered header portionthereof. Thus, for example, backwards compatibility may be maintainedwith legacy 802.11b devices while still providing enhanced throughputdemodulation capabilities.

In accordance with an embodiment of the invention, first data recoveryis performed using symbol correlation, including orthogonal class symbolcorrelation such as CCK correlation. Moreover, PSK demodulation here mayinclude utilizing DQPSK demodulation.

The present invention is further directed in part to a data packetincluding a header portion defining first PSK modulated data having afirst effective throughput, and a payload portion proceeding such headerportion, in which the payload portion includes, based on said headerportion, either second PSK modulated data having a second effectivethroughput at least five times the first effective throughput or symbolmodulated data having a third effective throughput, the third effectivethroughput being less than the second effective throughput. Inaccordance with an embodiment, this data packet may further include aDBPSK modulated preamble, and the PSK modulated data may include DQPSKmodulated data having an effective throughput of at least 22 Mbps.

Additional aspects and advantages of this invention will be apparentfrom the following detailed description of embodiments thereof, whichproceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of a transceiver according to anembodiment of the present invention.

FIG. 2 is a more detailed block diagram of a transmit baseband processorshown in FIG. 1.

FIG. 3 is a more detailed block diagram of a receive baseband processorshown in FIG. 1.

FIG. 4 diagrammatically illustrates a data packet format in accordancewith the embodiment of FIG. 1.

DETAILED DESCRIPTION

Turning now to the FIGs., FIG. 1 illustrates a wireless communicationstransceiver 100 according to an embodiment of the invention. In thisembodiment, inbound RF signals conveying a 802.11b compliant PLCP frameand/or a data packet formatted in accordance with the data packet format400 shown in FIG. 4 (“22 Mbps compatible data packet”) are picked up bythe duplex antenna 110 and routed to the RF receiver unit 115 of areceiver 150 arranged in a manner consistent with the present invention.The RF receiver unit 115 performs routine downconversion and automaticgain control of the inbound RF signals, and presents an analog basebandsignal containing the aforementioned 802.11b PLCP frame or data packetto the receive baseband processor 120. The functions of the receivebaseband processor 120 will be detailed below with reference to FIG. 3,including selective demodulation of the analog baseband signal torecover a 22 Mbps effective throughput inbound data bitstream from thepayload of a received 22 Mbps compatible data packet. Generallyspeaking, however, the receive baseband processor 120 performs symbolcorrelation and/or demodulation of the preamble, header and payloadportions of each inbound 802.11b PLCP frame or 22 Mbps compatible datapacket to recover bitstream data for receiver synchronization(preamble), frame or packet definition (header), or the actual inbounddata of interest (payload).

Once recovered by the receive baseband processor 120, the inbound datacontained in the PSDU of each received 802.11b PLCP frame or the payloadof the 22 Mbps compatible data packet is delivered to a networkinterface such as the MAC layer interface 125 and then on to higherlayer applications and devices being serviced by the transceiver 100.Here, the MAC layer interface 125 differs from a conventional 802.11bMAC layer interface in that it can accommodate inbound data at a 22 Mbpsmaximum rate, and includes logic in its PMD sublayer 130 to recognizewhen the payload of an inbound 22 Mbps compatible data packet includesDQPSK modulated inbound data in its payload portion with an effectivethroughput of 22 Mbps. As will be discussed in greater detail below withreference to FIG. 4, the PMD sublayer may conveniently recognize thishigh rate DQPSK mode through interpretation of a 22 Mbps transmissionrate in the Signal field 415 (e.g. 0xDC) as well setting a previouslyreserved bit in the Service field 420 of the inbound 22 Mbps compatibledata packet which are recovered prior to the start of actual payloadsymbol demodulation.

Outbound data intended for wireless transmission originating from thedevice(s) or application(s) being serviced by the transceiver 100 aredelivered to the transmit baseband processor 135 of the transmitter 160from the MAC interface 125. As before, the PMD sublayer 130 differs froma conventional PMD sublayer in that it can direct that outbound data bedelivered to the transmit baseband processor 135 at a 22 Mbpstransmission rate, and that the MAC interface 125 can selectivelyperform such transfer responsive to such directive or decision made bythe PMD sublayer 130. Directives from the PMD sublayer 130 expressingthe desired transmission mode, including the 802.11b 1, 2, 5.5 and 11Mbps effective throughput modes as well as the inventive 22 Mbps DQPSKmode are transferred to the transmit baseband processor as well for eachPLCP frame/packet, including the HI_SPEED semaphore discussed in greaterdetail with respect to FIG. 2. The transmit baseband processor 135formulates appropriate 802.11b PLCP frame or inventive data packetpreamble and header information, and symbol encodes the outbound data asspecified by the PMD 130 to generate a complete outbound 802.11b PLCPframe or data packet formatted in accordance with the data packet format400 of FIG. 4. As the frame or packet is being developed, it isconverted into analog form suitable for upconversion and RF transmissionby the RF transmitter unit 140 consistent with 802.11b physical layerrequirements.

Though not shown in FIG. 1, the transceiver 100 may form an operationalpart of a network interface apparatus such as a PC card or networkinterface card capable of interfacing with the CPU or informationprocessor of an information processing apparatus such as a desktop orlaptop computer, and may be integrated within and constitute a part ofsuch information processing apparatus. This network interface apparatusmay alternatively form an operational component of a wirelesscommunications access point such as a base station as will beappreciated by those ordinarily skilled in the art.

Turning now to FIG. 2, FIG. 2 is a more detailed block diagram of thetransmit baseband processor 135 shown in FIG. 1. So as not to obfuscatethe teachings of the present invention, several 802.11b compliantdirectives and signals are not shown. Outbound data in the form of MPDUpackets are sent by the MAC 125 at either 802.11b compliant 1, 2, 5.5 or11 Mbps selectable transmission rates/modes matching the effectivethroughput of the outbound PLCP frame, as well as 22 Mbps in the DQPSKtransmission mode of the present embodiment. The preamble and headerportions of the outbound 802.11b frame are generated by the preamblegenerator 210 and the header generator 212, which includes separateLength field 215, Service field 220, Signal field 225 and CRC 230generation units corresponding to the fields constituting the header ofthe 802.11b PLCP frame or 22 Mbps compatible data packet. Oncegenerated, the preamble, header and CRC (part of the header) aresequenced in frame order by the mux 235, followed by the outbound MPDUdata, which then undergoes routine scrambling/whitening using knowntechniques to optimize it for wireless transmission.

In contrast with a conventional 802.11b compliant header generationunit, the header generation unit 212 and the Signal generation unit 225in particular includes logic capable of interpreting an ENABLE_(—)22Mb_TX semaphore managed by the PMD 130 indicating whether or not thecurrent frame/packet will be transmitted in 22 Mbps DQPSK mode inaccordance with the present embodiment. If, for example, ENABLE_(—)22Mb_TX is false, the Signal generation unit 225 will insert theappropriate 802.11b compliant data rate into the Signal field of theoutbound PLCP frame. However, consistent with the data packet format 400shown in FIG. 4, if ENABLE_(—)22 Mb_TX is true, the 22 Mbps DQPSK modeis selected and so the Signal generation unit 225 will insert 0xDC (220in hexadecimal notation) into the Signal field 415 of the outbound datapacket. Though not shown in FIG. 2, in addition to or in thealternative, the Service generation unit 220 may include logic capableof setting at least one heretofore reserved bit in the Service field 420to indicate that the payload 435 arranged in accordance with the 22 MbpsDQPSK mode. More detail on the data packet format 400 will be providedbelow with reference to FIG. 4.

Once generated, the scrambled preamble, header and payload portionsdefining a current outbound PLCP frame or 22 Mbps compatible data packetare serially presented to the symbol encoding unit 251, here showncontaining a DBPSK modulation pathway (including DBPSK modulator 250,mux 255 and Barker spreader 260) for preamble encoding and parallelDQPSK (DQPSK modulator 265, mux 255 and the Barker spreader 260, withthe DQPSK modulator 265 being clocked at 1 MHz e.g. the CLK_SELECTsemaphore is clear) and DBPSK modulation pathways for short/long headerencoding respectively. These modulation pathways are used to encode theoutbound data received from the MAC interface 125 when legacy base802.11 1 Mbps (using the DBPSK modulator pathway) and 2 Mbps (using theDQPSK modulation pathway) transmission rates/modes are desired. For 5.5and 11 Mbps rates compliant with 802.11b, a CCK modulator 270 is usedclocked at the 11 MHz chipping rate.

When it is desired to transmit the outbound data at an effectivethroughput 22 Mbps, thereby doubling the 802.11b 11 Mbps maximum, inaccordance with this embodiment, the 11 MHz chipping clock is applied tothe DQPSK modulator 265. Since each DQPSK sample can encode 2 bits ofoutbound data, this results in a 22 Mbps throughput. The 11 MHz clock isapplied through the modulation control unit perceiving the HI_SPEEDsemaphore from the PMD sublayer 130 as being set and consequentlysetting the CLK_SELECT signal to a logic level (e.g. true) directing themux 245 to direct the 11 MHz clock to the clock input of the DQPSKmodulator 265 as it received the scrambled outbound data. Line 267communicatively couples the output of the DQPSK modulator to themodulation selection mux 275 to complete the 22 Mbps mode DQPSKmodulation pathway.

The modulation control unit 290 drives the MOD_SELECT signal, which isused in conjunction with the conventional long/short signal to have mux255 and mux 275 select which of the four possible modulation pathwaysdescribed above should be used to develop the symbol encoded preamble,header and payload of the outbound 802.11b PLCP frame or 22 Mbpscompatible data packet. For example, when generating an 11 Mbps mode802.11b PLCP frame, the modulation control unit asserts e.g. “00” toselect the DBPSK pathway to generate the symbol encoded preamble 410 andthe PLCP header 440 (if a short preamble is desired, the DBPSK pathwayis used only for the short preamble, and the mux 255 selects the DQPSKmodulator 265 output when clocked to 1 MHz to develop the symbol encodedPLCP header). As such, the modulation control unit 290 will then asserte.g. “10” on the MOD_SELECT line during the payload portion part of thePLCP frame generation sequence to deliver CCK modulated outbound data tothe FIR 280, digital-to-analog converter or DAC 285, and onto the RFtransmitter unit 140.

If, however, a 22 Mbps compatible data packet is to be transmitted, themodulation control unit 290 instead asserts e.g. “01” on the MOD_SELECTline during the payload portion part of the data packet generationsequence to select output from the 22 Mbps DQPSK modulation pathway todeliver DQPSK modulated symbols at 11 MHz to the FIR 280 and DAC 285.

Though the present embodiment contemplates a dual role, dual clockedDQPSK modulator 265, in fact in an alternative embodiment, separateDQPSK modulators (1 clocked at 1 MHz, the other clocked at 11 MHz) maybe provided to undertake the necessary DQPSK modulation activitiesspecified herein.

Turning now to FIG. 3, FIG. 3 is a more detailed block diagram of thereceive baseband processor 120 shown in FIG. 1. As such, an analogbaseband signal conveying an inbound 802.11b PLCP frame or 22 Mbpscompatible data packet recovered by the RF receiver unit 110 of thereceiver 150 is fed to the input of the analog to digital converter 310to convert it into digital form. With the aid of the 44 MHz clock, theADC produces a corresponding digital signal sampled at 44 MHz. Next,this digital signal passes through the digital FIR LPF 315 to rejectout-of-band interference, and the down sampler 320 to provide a 22 MHzdigital signal bearing the frame/packet of interest.

This 22 MHz signal next encounters two parallel baseband demodulationpathways. The first demodulation pathway, including the Barkercorrelator 330, down sampler 335, Rake 340 and the down sampler 345 isused to recover a despread 1 MHz signal representing the preamble andheader portions of the inbound frame or data packet for symboldemodulation by the combination DBPSK/DQPSK demodulator 375. This firstdemodulation pathway-demodulator combination 375 is also used for symboldecoding a base 802.11 PLCP frame payload in 1 Mbps/2 Mbps modes. Thesecond demodulation pathway is used to symbol demodulate a high rate802.11b payload portion of the inbound frame as well as the 22 MbpsDQPSK mode modulated payload for an inbound 22 Mbps compatible datapacket, and includes a 22 MHz to 11 MHz down sampler 350 following by adecision feedback equalizer 355. To begin the CCK symbol decode processfor 802.11b compliant payloads at 11 Mbps or 5.5 Mbps transmissionmodes, a CCK correlator 360 is provided. It should be noted that, inaddition, a parallel pathway 357 that bypasses this correlator 360 isprovided to deliver a 22 Mbps DQPSK modulated payload directly to theDBPSK/DQPSK demodulator 375.

A demodulation controller 365 is used to control which demodulationpathway should be used via the DEMOD_SELECT control line coupled to thecontrol element mux 370, based on which portion of the inbound frame orpacket is being demodulated, as well whether 5.5 Mbps+ payloadmodulation modes are specified. To this end, the demodulation controllerbases its DEMOD_SELECT decision based on the conventional HI_RATE PSDUsemaphore, generated by the known rx state machine 372 in conjunctionwith appropriate signaling issued by the MAC interface 125, whichdetermines whether the 802.11b high rate PHY transmission modes arespecified, along with the inventive ENABLE_(—)22 Mb_RX semaphore (set if22 Mbps DQPSK mode according to the present invention is specified).Though not required, in this embodiment, the ENABLE_(—)22 Mb_RXsemaphore is managed as a register within the MAC I/F 125 by the PMDsublayer 130. The combination DBPSK/DQPSK demodulator 375 is used torecover the symbol encoded inbound data presented in the preamble,header and payload portions, including the 22 Mbps payload modeconsistent with the present invention. The DBPSK/DQPSK demodulator isclocked at the symbol rate; i.e., 1 MHz for 1 Mb and 2 Mb modes, and1.375 MHz for 5.5 Mb and 11 Mb modes, and 11 MHz for 22 Mb mode.

After symbol demodulation, the recovered inbound data is descrambled bythe descrambler 380 in a known fashion, and delivered to the MACinterface 125 (FIG. 1).

FIG. 4 illustrates the data packet format 400 used by the transceiver100 of FIG. 1 to support the 22 Mbps DQPSK transmission mode, inaddition to 802.11b and base 802.11 modes. To this end, the data packetformat 400 specifies an 802.11b compliant PLCP preamble portion 410 andcan support either long or short formats. The next portion, the PLCPheader 440, includes an 8 bit Signal field 415, 8 bit Service field 420,16 bit Length field 425, and 8 bit Frame check sequence 430. Like the802.11b compliant PLCP header, the header portion 440 can be transmittedat 1 Mbps (DBPSK modulation at 1 MHz) or 2 Mbps (DQPSK modulation at 1MHz) effective throughput. Moreover, in this embodiment, the Signalfield 415 differs from an 802.11b compliant Signal field only in that itis additionally capable of specifying the 22 Mbps data rate 0xDC or 220in hexadecimal notation. Though not required, one or more heretoforereserved bits in the Service field 420 are used in this embodiment toindicate that the payload 435 is modulated in accordance with theabove-described 22 Mbps mode.

The Length 425 and Frame Check Sequence 430 fields are formatted inaccordance with corresponding fields in the 802.11b compliant PLCPheader. The PSDU 435 contains the payload modulated in accordance withone of the legacy 802.11b modes (1/2/5.5/11 Mbps) or the 22 Mbps modeconsistent with the present invention as specified in the Signal 415and/or Service 420 fields.

Thus, this data packet format 400 is backwards compatible with the base802.11 and 802.11b standards, and would only deviate from the standard802.11 and 802.11b PLCP frame formats only where the 22 Mbps DQPSKtransmission mode according to the present embodiment is selected.Furthermore, a legacy 802.11b device would, upon decoding andinterpretation of the Signal 415 and Service 420 fields, consider aninbound packet formatted in accordance with packet format 400 as anunrecognizable, illegal or garbled 802.11b packet, or possibly even asinterference and would thus ignore the packet. The 22 Mbps transmitterwould then back-off to legacy 802.11b CCK 11/5.5 Mbps modes in a knownmanner to retransmit the data of interest.

It will be obvious to those having skill in the art that many changesmay be made to the details of the above-described embodiments of thisinvention without departing from the underlying principles thereof. Thescope of the present invention should, therefore, be determined only bythe following claims.

What is claimed is:
 1. A baseband processor comprising: an analog todigital converter configured to convert a baseband signal from an analogformat into a corresponding digital format, wherein the baseband signalcomprises a data packet having i) a preamble portion, ii) a headerportion, and iii) a payload portion, wherein the payload portion of thedata packet is in accordance with either i) a first format or ii) asecond format, and wherein the second format is associated with a higherdata rate than the first format; a parallel demodulation pathwayconfigured to receive the baseband signal in the corresponding digitalformat, wherein the parallel demodulation pathway includes a firstdemodulation pathway configured to recover i) the preamble portion ofthe data packet, ii) the header portion of the data packet, and iii) thepayload portion of the data packet in response to the payload portion ofthe data packet being of the first format; and a second demodulationpathway configured to recover the payload portion of the data packet inresponse to the payload portion of the data packet being of the secondformat.
 2. The baseband processor of claim 1, wherein the data packet iscompliant with IEEE Standard 802.11b.
 3. The baseband processor of claim1, wherein: a data rate of the first format corresponds to 11 Mbps; anda data rate of the second format corresponds to 22 Mbps.
 4. The basebandprocessor of claim 1, further comprising a demodulator configured todemodulate the payload portion of the data packet in the first format orthe second format.
 5. A transceiver comprising the baseband processor ofclaim
 1. 6. A network interface apparatus comprising the transceiver ofclaim
 5. 7. The network interface apparatus of claim 6, wherein thenetwork transceiver apparatus comprises a PC card or a network interfacecard.
 8. An information processing apparatus comprising the networkinterface apparatus of claim
 7. 9. The information processing apparatusof claim 8, wherein the information processing apparatus comprises alaptop computer or a desktop computer.
 10. A method comprising:converting a baseband signal from an analog format into a correspondingdigital format, wherein the baseband signal comprises a data packethaving i) a preamble portion, ii) a header portion, and iii) a payloadportion, wherein the payload portion of the data packet is in accordancewith either i) a first format or ii) a second format, and wherein thesecond format is associated with a higher data rate than the firstformat; and recovering, in a first demodulation pathway, i) the preambleportion of the data packet, ii) the header portion of the data packet,and iii) the payload portion of the data packet in response to thepayload portion of the data packet being of the first format; andrecovering, in a second demodulation pathway, the payload portion of thedata packet in response to the payload portion of the data packet beingof the second format.
 11. The method of claim 10, wherein the firstdemodulation pathway is separate from the second demodulation pathway.12. The method of claim 10, wherein the data packet is compliant withIEEE Standard 802.11b.
 13. The method of claim 10, wherein: a data rateof the first format corresponds to 11 Mbps; and a data rate of thesecond format corresponds to 22 Mbps.
 14. The method of claim 10,further comprising demodulating the payload portion of the data packetin the first format or the second format.